Industrial process for extracting rhenium



Dec. 18, 1951 M. M. BHERTQLUS I ,1

INDUSTRIAL PROCESS FOR EXTRACTING RHENIUM Filed March '27, 1948 2 SHEETSSHEET 1 Fig 1 J77 venfor Marcel M 12/16! Barb/14 Dec. 18, 1951 M. M. BERTOLUS 2,579,107

INDUSTRIAL PROCESS FOR EXTRACTING RHENIUM Filed March 27. 1948 2 SHEETS-SHEET 2 Patented Dec. 18, 1951 'mnvsrenu. 1 1 66388 F RHENIUM: MarcelMrBertolus, relegate f T Application Mal-011 27, 194s; Sfiaf g The presentinvention relates to an industrial process for the recovery of rhenium which'exists in nature in very Small quantities in certain ores where it is associated in the form of rh'enium sulfide with natural molybdenum sulfide (molybf denite); It is known that the volatile oxide Hegoq can b'e'produced by roasting pure rh'eniju'm sulfide at a temperature as low as 200-300- C'. in thepresenc'e of air or oxygen, 1. e. at a temperature lower than that, of volatilization of the molybdenum oxide'which' is" known to be 700 C'. It' has" been accordingly suggested to produce rheni'um oxide by heating molybdenite in the.

presence of air or oxygenat' a temperature comprised between 200 and 300 C.

I have discovered however that, contrary to what might be expected, the rhenium sulfide does n'otbehave in' the manner stated above in the presence of molybdenum sulfide and-that oxidation of rhenium sulfide" does not take'pla'ce' H presence of molybdenum sulfide at temperatures 7 even above those which would startthe reaction in" the absence of the molybdenum sulfid'ef Fur} thermore, if the temperature isr'aised sumeient: ly to "start the reaction, productionof S02 takes place first; causing a mechanical entrainment of molybdenum compounds, particularly of Mesa dust which contaminates the rhenium' oxide R6207; If the" temperature is too high, volatilize;- tion" ofmolybdenum trioxyde M003 is produced simultaneously. a

The object of the present invention is'laf selective extraction ,of rhenium oxide by roasting m'olybdenite containing traces of rhenium sulfidexw .7

Another object of the invention to avoid,

whenthus roasting molybdenite; a large dilution of 'rhe'nium caused by an important flowof S02 whichwould contaminate the rhenium oxide by MoSz entrained in the form of a fine dust. 1

8- claims. (Cl. 52.55-1 .39!)

A further object of the invention is to main- 7 tain the rhenium content ashigh as possible at? the invention is the extractionoff rheniurii from copper-molybdenum sulfide ores which are first 1 subjected to selective flotation for producinga molybdenite concentrate. 4

With these andother'objects in View, the process'according to the invention comprises', 'fas a firstphase, the heating of the molybdenite inan'" oxidizing atmosphere to a temperature above 500"; maintaining this temperature "by combus' tiorr of the combined sulfur until substantially" all sulfur nae been-eliminated as sulfur Id-ie eficei lectifig' tlfe gases: evolvedduring the t; separatingmolybden-i'te: returning same into; th'e-Ipreces' new, as a second phase, supplying: extrn'ar tomaintain the material at a tem-- erattre as e approxnnam 550 C. but below the temperature ofvolatilization of molybdenunr oxide; and" supplying oxygen, whereby the compounds are oxidized to' R620? and; the lattervolatilizedi whileentrainment? of the molybdenum oxide" the evolved gases is precluded-by afu'sing together of the molybdenum oxide" particles} collect g s'e'paraitely thegasesr evolved during this second phase ofthe process; and separating the rhen-i-um' oxide therefromm :4-

Ap'plican'thasdisooveredthatz (1.)- The volatilizatibn 6f 'rh ni'um' oxide only starts after the sulfurof; the molybdenite 'hasf been shbstanti'aHy eliminated as sulfur dioxide-.5 II 7 '(21) ecessary to' raisethe temperature" above 500" C: in -order to cause the" volatiliza'tlonn omelet. a 1 "(3.) "The temperature has to'beraised to- "at-f least 550 Gk (bfitbblew' '700 Which id'the V019, tilizatibri pbil'lt'of molybdenum Oxide) 'betiallse at 550 C.- the crystals or the mybden'um' Oxide begin t 0' sinter; thus-forming' a-"po'rou's permeable mass anew-mg the 'rhenilimhptdXydetUSCap frelii'but prvefiting-niechameafefltraimiientdff ,taineda'sthe by prdduct; of" the manufactu e of L contenti'vair-yingfreifit hdo otb te /eoc odag v Furthermore th tw'o steptreatment accord e lum of a 1. a. 4 V, rh'enium Oiiide isjr'educ'ed n'ra very' conside proportion and th t furthermore the said are, as stated above fre'e oif'niolybdenite' 'du's't', fr of fluorhydric acidand" nee I of oil vapour" (oil used the fibtatidli: treatment) which ari d velo'ped at the" begimiin for' the roasting treat-.

,ment. v

As shown on Fig. 1, this installation comprises a rotary kiln I in which a load of molybdenite is preferably separated from its copper sulphide and which is supplied with hot air from a hoteair drier 2 and a preheater 3, for instance an, electrical preheater. At the outlet of the kiln a dust chamber 4 is provided on which are branched two distinct circuits for the evacuation of the gases developed by roasting through the chimney 5, the said "circuits being put separately in service according to requirement. The first of those circuits-is branched on chamber 4 during the first period of the. roasting, treatment and comprises several dust extractors, for instance three cyclones B, 6', 6'! in whichmolybdenite dust sucked by gases is precipitated, the said cyclones being preceded by an air inlet I for cooling. U

The second evacuation circuit is branched on chamber 4 during the second period of the roasting treatment and is arranged for the extraction ofa rheniumoxide.v It comprises an air inlet 8 for cooling, a separator, for. instance a multicyclone .S'kept at a, suflicientlyhigh temperature so thatthe rhenium oxide vapors cannot condense in it, :for instance from 250? to 300 C., a scrubber tower 10, preferably provided with a sprayer for the injection ofthe solvent intended to dissolve the rhenium oxide. The said solvent is preferably water. or a highly, diluted base andcirculates along a closedcircuit in which it is discharged by a pump. H in. order toobtain in tank [2 as higha concentrated solution as possible of rhenium oxide which. fac litates he ex a tionn th er y a known process. Following thescr'ubber tower l0, a second cyclone I3 is provided for the purpose of recuperating the liquid drops sucked into the said scrubbertower by the draft of gases. According to an, alternative not shown on the drawing the scrubber tower may, be followed by a Cottrel separator in which the separation of the rhenium oxide is b e ,e t at pall y i parti electric charges to thev said rhenium oxide, the said charges causingits deposit in the'apparatus.

.This installation operates as follows: V

Assuming the kiln to be loaded with molyb-- denite, the whole of the electrical energyayailable put on the electrical air preheaterin order to carrythe massin the kiln to the temperature at which the reactionisstarting. V, ,7 7

As soon as the oxidation of molybdenite has begun and when temperature rises on account of the heat developed bythe reaction, the electrical power on the preheater is lowered. Also the air supply isadjusted so that thetemperature in the To collect the latter product the first gas circuit is closed and the exhaust circuit 89lll-|3 is opened.

The installation shown on Fig. 2 differs from that described above in that it comprises a continuous roasting kiln I4 instead of a discontinuous rotary kiln, for instance a kiln of the Nichols- I-Ierreshoff type comprising a number of hearth plates I5 to.25v heated by electrical devices or by as or fuel oil distributors not shown on the drawing. The molybdenite loaded on those plates is mixed during roasting by scrapers which make it i t d d, the said molybdenitehavingbeen come down from one sole to another (according to the path shown on the drawing in dotted lines) as roasting is progressing, the molybdic acid being finally evacuated through the outlet provided at the bottom of the kiln. A few last soles of that furnace,for instance the two lower sole 24,

kilnf'does not eXcredfiOO 0, During that period 7 of the process, the gases dieveloped by roasting are evacuated through circuitli, 6 6". V

At the end of the treatment, when most of the sulphur has been eliminated the temperature drops in the kiln; Then the ielectri'cal' power supplied to the preheater is'raisedagfain inorder to bringthat temperature back'to 'about'600" C.

in order to obtain acomplete oxidation of rhenium and a complete sublimation of its oxide Rezqv.

upon which molybdenite falls at the end of the toasting treatment are kept at a temperature of 550. C. to 600 C. and the gases which are developed by the roasting of the mass on the two latter soles are sucked in the exhaust circuit 8--9-l0l3 which is strictly the same as above, while the gase developed on the upper soles are sucked in the exhaustcircuit 166"6.

In both cases, the molybdenite dust which d-Q posits in the cyclones 6, 6, 6" are recuperated and turned back to the kiln l or [4 with at the same time a certain quantity of rhenium oxide which may escape from the kiln in the earlier period of the toasting treatment. To this Iend,.temperature is lowered in the multicyclonesforfobtaining the condensation of R207 at the same time" as the deposit f the molybdenite dust.

What I claim is: 1. Industrial process for the extraction of rhenium from molybdenite concentrate contain-i ing traces of rhenium sulfide comprising, as a first phase, the heating of the concentrate in an oxidizing atmosphere to a temperature above 500? C.', maintaining this temperature by combustion of. the combined sulfur until substan tially all the sulfur has been eliminated assulfur dioxide, collecting the gases evolved during the first phase of treatment, separating the I molybdenite dustcontained therein and returning same" into the process, then, as a second phase, supplying external heat to maintain the materialat a temperature, above approximately 550C. but below the temperature of volatiliz a- 1 tion of molybdenum oxide, and supplying oxygen whereby the rhenium compounds are oxidized to Re20'z and the latter volatilized, while entrainment of the molybdenum oxide in the evolved gases is precluded by. a fusing together of th e molybdenum oxide particles, collecting separately the gases evolved during this second phase therefrom.

2. Industrial process for the extraction of of the pro'cesaand separating the rhenium oxide rhenium, from molybdenite concentrate containe .1 ing traces of rhenium sulfide comprising, as a first phase, heating the concentrate in an oxidiz 1 ing atmosphere by combustion of the combined sulfur to a temperature betweenv 500? C. and

600?v (Land maintaining this temperature until substantially all theSuIfur has been eliminated as sulfur dioxide, collecting the gases evolved duringthis first phase. of treatment, separating ing atmosphere by' combustion "of the combined.

sulfur to a temperature between 550 C. and 600 C. and maintaining this temperature until substantially all the sulfur *has been eliminated as'sulfur dioxide, collectingthegasesev'olved' during this first phase of treatment; separating the molybdenite dustcontained" therein and returning same into the process, then, as a second phase, supplying external heat to maintain the material at a temperature above approximately 550 C. but below the temperatureof volatilization of the molybdenum oxide and supplying oxygen-containing gas whereby the rhenium compounds are oxidized to Rezow and the latter is volatilized, while entrainment of the molybdenum oxide in the evolved gases is inhibited by a fusing together of the molybdenum oxide particles, collecting separately the gases evolved during this second phase of the process and scrubbing said gases with a highly diluted base to dissolve the rhenium oxide.

4. Industrial process for the extraction of rhenium from molybdenite concentrate containing traces of rhenium sulfide comprising, as a first phase, heating the concentrate in an oxidizing atmosphere by combustion of the combined sulfur to a temperature between 550 C. and 600 C. and maintaining this temperature until substantially all the sulfur has been eliminated as sulfur dioxide, collecting the gases evolved during this first phase of treatment, separating the molybdenite dust contained therein and returning same into the process, then, as a second phase, supplying external heat to maintain the material at a temperature above approximately 550 C. but below the temperature of volatilization of the molybdenum oxide and supplying oxygen-containing gas whereby the rhenium compounds are oxidized to RezO'z and the latter is volatilized, while entrainment of the molybdenum oxide in the evolved gases is inhibited by a fusing together of the molybdenum oxide particles, collecting separately the gases evolved during this second phase of the process and scrubbing said gases with water to dissolve the rhenium oxide.

5. Industrial process for the extraction of rhenium from molybdenite concentrate containing traces of rhenium sulfide comprising, as a first phase, heating the concentrate in an oxidizing atmosphere to a temperature between 550 C. and 600 C. by combustion of the combined sulfur and maintaining this temperature until substantially all the sulfur has been eliminated as sulfur dioxide, collecting the gases evolved during this first phase of treatment, separating the molybdenite dust contained therein and returning same into the process, then, as a second phase, supplying external heat to maintain the material at a temperature above approximately 550 C. but below the temperature of volatilization of the molybdenum oxide and supplying oxygen-containing gas whereby the rhenium compounds are oxidized to RezOwandthezlatter is" volatilized, while entrainment of the molyb' denumoxide intheevolved gases is precludedby a fusing. together of the molybdenum oxide par ticles, collecting separately the gases evolved during this secondphase of the process, bringing them. into intimate contact with a finely divided and highly dilutedbase dissolving the rhenium oxide and separating the droplets of the: solution thus obtained from the insoluble residual gaseous phase. I I

6. Industrial process for the extraction of rhenium from molybdenite concentrate containing traces of rhenium sulfide comprising, as a first phase, heating the concentrate in an oxidizing atmosphere to a temperature between 550 C. and 600 C. and maintaining this temperature bycombustion of the combined sulfur untilisub-' stantially all the sulfur has been eliminated as sulfurdioxide, collecting the gases evolved during this first phase of treatment, separating the molybdenite .dust contained therein and returning same into the process, then, as a second phase, supplying external heat to maintain the 1 material at a temperature above approximately;

550 C. but below the temperature of volatilization of the molybdenum oxide and supplying oxygen-containing gas whereby the rhenium compounds are oxidized to R8207 and the latter is volatilized, while entrainment of the molybdenum oxide in the evolved gases is precluded by a fusing together of the molybdenum oxide particles, collecting separately the gases evolved during this second phase of the process, cooling said separately collected gases, bringing them into intimate contact with a finely divided and highly diluted base dissolving the rhenium oxide, imparting electric charges to the droplets of the solution thus obtained and separating same from the insoluble gaseous phase by electrostatic separation.

'7. Industrial process for the extraction of rhenium from copper-molybdenum sulfide ores, comprising a preliminary step consisting in the production of a molybdenite concentrate containing traces of rhenium sulfide by selective flotation of said ore, then, as a first phase, heating said concentrate in an oxidizing atmosphere to a temperature above 500 C. and maintaining this temperature until substantially all the sulfur has been oxidized to sulfur dioxide, collecting the gases evolved during this first phase of treatment, separating the molybdenite dust contained therein and returning same into the process, then, as a second phase, supplying heat to maintain the material at a temperature above approximately 550 C. but below the temperature of volatilization of the molybdenum oxide and supplying oxygen-containing gas whereby the rhenium compounds are oxidized to R820: and the latter is volatilized, while entrainment of the molybdenum oxide in the evolved gases is inhibited by a fusing together of the molybdenum oxide particles, collecting separately the gases evolved during this second phase of the process and separating the rhenium oxide therefrom.

8. Industrial process for the extraction of rhenium from copper-molybdenum sulfide ore containing traces of rhenium sulfide, comprising a preliminary step consisting in the concentrat ing of molybdenite by a selective flotation of said ore, said traces of rhenium sulfide being contained in the concentrates, heating of the molybdenite concentrates during a first phase of treatment in an oxidizing atmosphere to a temperatureibetween 550 0. and 600 0. andmaine taming this temperature by combustion of the combined sulfur until substantially all thesulfur;

has been eliminated as sulfur dioxide, collecting.

the gases evolved during this first phase of treatment, separating the molybdenite dust contained therein and returning same into the process, then, as a second phase, supplying external heat to maintain the material at a temperatureabove approximately 550 C. but below the temperature of volatilization of the molybdenumoxide and supplying oxygen-containing gas whereby the rhenium compounds are oxidized to M201 and the latter is volatilized, while entrainment of the molybdenum oxide in the evolved gases is inhibited by a fusing together of the molybdenum oxide particles into a porous and permeable, nondusting mass, collecting separately the gases evolved during this second phase of the process,

cooling said separately collected gases, bringing 2o REFERENCES mm 7 I The following references are of record in the file of this patentz- V.

UNITED STATES PATENTS 0 A v Date '1 Number Name 1,118,150 Robertson Nov. 24,- 1914 1,371,995 Nesbit Mar. 15, 1921 1,888,996 McInery et a1. Nov. 29,1932 1,911,943 Driggs 1 May 30, 1933 Roetheli June 17, 1947 OTHER REFERENCES Perry, Chemical Engineers Handbook, 2nd ed 1941, sect. 15, pages 1850-1884.

Taggert,. Handbook of Mineral Dressing, 1945 

1. INDUSTRIAL PROCESS FOR THE EXTRACTION OF RHENIUM FROM MOLYBDENITE CONCENTRATE CONTAINING TRACES OF RHENIUM SULFIDE COMPRISING, AS A FIRST PHASE, THE HEATING OF THE CONCENTRATE IN AN OXIDIZING ATMOSPHERE TO A TEMPERATURE BY COM500* C., MAINTAINING THIS TEMPERATURE BY COMBUSTION OF THE COMBINED SULFUR UNTIL SUBSTANTIALLY ALL THE SULFUR HAS BEEN ELIMINATED AS SULFUR DIOXIDE, COLLECTING THE GASES EVOLVED DURING THE FIRST PHASE OF TREATMENT, SEPARATING THE MOLYBDENITE DUST CONTAINED THEREIN AND RETURNING SAME INTO THE PROCESS, THEN, AS A SECOND PHASE, SUPPLYING EXTERNATAL HEAT TO MAINTAIN THE MATERIAL AT A TEMPERATURE ABOVE APPROXIMATELY 550* C. BUT BELOW THE TEMPERATURE OF VOLATILIZATION OF MOLYBDENUM OXIDE, AND SUPPLYING OXYGEN WHEREBY THE RHENIUM COMPOUNDS ARE OXIDED TO RE207 AND THE LATTER VOLATILIZED, WHILE ENTRAINMENT OF THE MOLYBDENUM OXIDE IN THE EVOLVED GASES IS PRECLUDED BY A FUSING TOGETHER OF THE MOLYBDENUM OXIDE PARTICLES, COLLECTING SEPARATELY THE GASES EVOLVED DURING THIS SECOND PHASE OF THE PROCESS, AND SEPARATING THE RHENIUM OXIDE THEREFROM. 